| Competition: | K3 League |
| Season: | 2020 |
| Dates: | 16 May – 5 September 2020 |
| Winners: | Gimhae FC (1st title) |
| Relegated: | Chuncheon Citizen Jeonju Citizen |
| Matches: | 119 |
| Total Goals: | 430 |
| Best Player: | Choi Yong-woo[1] |
| League Topscorer: | Choi Yong-woo (15 goals) |
| Biggest Home Win: | KHNP 7–0 Yangju |
| Biggest Away Win: | Yangju 0–5 Changwon |
| Prevseason: | 2019 National League |
| Nextseason: | 2021 |
The 2020 K3 League was the first season of the K3 League as a semi-professional league. After the 2019 season, the former Korea National League and K3 League Advanced went defunct and rebranded as the K3 League.
Eight National League teams, six K3 League Advanced teams and two K3 League Basic teams entered in the 2020 season.[2] The 16 participating teams were divided into two groups, the top eight and the bottom eight, after playing each other once. Each team played 22 matches including 7 group stage matches. The 15th and 16th-placed teams were directly relegated to the K4 League, and the 14th-placed team advanced to the relegation play-off.[3]
| Club | City | Stadium | Capacity | |
|---|---|---|---|---|
| Busan Transportation Corporation | Busan | Busan Gudeok Stadium | 24,363 | |
| Changwon City | Changwon | Changwon Football Center | 15,116 | |
| Cheonan City | Cheonan | Cheonan Football Center | 15,500 | |
| Cheongju FC | Cheongju | Cheongju Stadium | 17,264 | |
| Chuncheon FC | Chuncheon | Chuncheon Stadium | 20,000 | |
| Daejeon Korail | Daejeon | Daejeon Hanbat Sports Complex | 17,371 | |
| Gangneung City | Gangneung | Gangneung Stadium | 33,000 | |
| Gimhae FC | 25,000 | |||
| Gimpo Citizen | Gimpo | Gimpo Sports Complex | 5,068 | |
| Gyeongju Citizen | Gyeongju | Gyeongju Civic Stadium | 12,199 | |
| Gyeongju KHNP | Gyeongju | Gyeongju Civic Stadium | 12,199 | |
| Hwaseong FC | Hwaseong | Hwaseong Stadium | 35,270 | |
| Jeonju Citizen | 30,000 | |||
| Mokpo City | Mokpo | 5,952 | ||
| Pyeongtaek Citizen | Pyeongtaek | 15,000 | ||
| Yangju Citizen | Yangju | 5,000 |
| Club | Player 1 | Player 2 | Player 3 | AFC player | Former players |
|---|---|---|---|---|---|
| Changwon FC |  Takuma Ishibashi | ||||
| Cheonan City | Jerry van Ewijk | ||||
| Gimhae FC |  Carlinhos | ||||
| Gimpo Citizen |  Ismael Jorge Balea | ||||
| Hwaseong FC |  Olivier Bonnes | ||||
| Pyeongtaek Citizen | Matheus | Wictor Hugo |  Abdoulie Gomez | Hirotomo Kawazu | |
| Yangju Citizen | Martin Sawi | Paul Puk Kun Pal | |||
After 15 matches, the league splits into two sections of eight teams each, with teams playing every other team in their section once (either at home or away). The exact matches are determined upon the league table at the time of the split.
When the first round and semi-final matches were finished as draws, their winners were decided on the regular season rankings without extra time and the penalty shoot-out.[4]
----Gimhae FC won 2–1 on aggregate.
The relegation play-off (K4 League promotion play-offs final) was contested between the 14th-placed team of K3 League and the winners of K4 League play-off (semi-final). When the match was finished as a draw, both clubs remained in their respective leagues.